1. Field
The present disclosure relates generally to communications systems, and more specifically, to an apparatus and method of modulating an amplitude, phase, or both the amplitude and phase of a substantially periodic signal on a per cycle basis.
2. Background
Communications devices that operate on limited power supplies, such as a battery, typically use techniques to provide the intended functionality while consuming relatively small amounts of power. One technique that has been gaining in popularity relates to transmitting signals using pulse modulation techniques. This technique generally involves transmitting information using low duty cycle pulses and operating in a low power mode during times when not transmitting the pulses. Thus, in these devices, the efficiency is typically better than communications devices that operate a transmitter continuous.
Usually, these low power communications devices have strict transmission specification requirements dictated typically by governmental agencies. In order to ensure that governmental requirements are met as well as to more precisely transmit and receive signals among communications devices, the frequency components or spectrum of the pulses transmitted should be accurately controlled. Each of the transmitted pulse may include a plurality of cycles of a periodic signal, such as a sinusoidal signal. Thus, in order to control the frequency components or spectrum of the pulses, the amplitude and/or phase of the periodic signal should be controlled to meet the requirements. Additionally, since each pulse may only comprise a few cycles of a periodic signal, the control of the amplitude and/or phase of the signal should have relatively fine resolution, such as on a per cycle basis.